The present invention relates generally to medical methods, devices, and systems for the endovascular, percutaneous or minimally invasive surgical treatment of bodily tissues, such as tissue approximation or valve repair. More particularly, the present invention relates to repair of valves of the heart and venous valves.
Surgical repair of bodily tissues often involves tissue approximation and fastening of such tissues in an approximated arrangement. Tissue approximation includes coapting the leaflets of the valves in a therapeutic arrangement which may then be maintained by fastening or fixing the leaflets via the use of an implanted fixation device. Such coaptation can be used to treat regurgitation which most commonly occurs in the mitral valve and tricuspid valve of the human heart.
During normal operation of the heart, the valve leaflets of the mitral valve open during diastole when the left atrium of the heart is filled with blood allowing the blood to pass into the left ventricle. During a normal cycle of heart contraction (systole), the valve leaflets are pushed together such that the free edges of the leaflets are closed against each other along a line of coaptation to prevent the back-flow or “regurgitation” of blood into the left atrium. In this fashion, the mitral valve functions as a “check valve” or “one-way valve” which closes the opening of the valve to prevent back-flow of oxygenated blood into the left atrium when the pressure developed in the left ventricle exceeds the pressure in the left atrium. In this way, oxygenated blood can be effectively pumped from the left ventricle into the aorta through the aortic valve. Regurgitation can significantly decrease the pumping efficiency of the heart, placing the patient at risk of severe, progressive heart failure.
The mitral valve leaflets are attached to the surrounding heart structure along an annular region referred to as the valve annulus. The free edges of the leaflets are secured to the lower portions of the left ventricle through tendon-like tissue structures known as chordae tendineae or chordae. The chordae are attached to the papillary muscles which extend upwardly from the lower portions of the left ventricle and interventricular septum.
Mitral valve regurgitation can result from a number of different mechanical defects in the mitral valve or the left ventricular wall. The valve leaflets, the valve chordae which connect the leaflets to the papillary muscles, the papillary muscles or the left ventricular wall may be damaged or otherwise dysfunctional. Commonly, the valve annulus may be damaged, dilated, or weakened, limiting the ability of free ends of the leaflets of the mitral valve to close adequately against each other due to the high fluid pressures that can develop in the left ventricle during systole.
Common treatments for mitral valve regurgitation rely on valve replacement or repair of damaged leaflets, along with annulus remodeling which is generally referred to as valve annuloplasty. Additional techniques for mitral valve repair rely on suturing adjacent segments of the opposed valve leaflets together and is referred to as the “bow-tie” or “edge-to-edge” technique. While all these techniques can be very effective, they usually rely on open heart surgery where the patient's chest is opened, typically via a sternotomy, and the patient placed on cardiopulmonary bypass. The need to both open the chest and place the patient on bypass is traumatic and has associated high mortality and morbidity. Accordingly, successful methods have been developed for performing less invasive repairs to the mitral valve in order to avoid the open heart procedure. Such repair procedures also can be performed on a beating heart such that the patient does not have to be placed on cardiopulmonary bypass.
These less invasive procedures for mitral valve repair rely on the introduction of instruments via a transcatheter procedure in which an opening is made into the wall of heart that allows the instruments to enter the heart, usually in the left or right atrium. Suitable gripping and fastening instruments have appropriate dimensions to fit through a cardiac guide catheter into the heart. The methods of repair of the mitral valve typically include gripping the edges of the two leaflets of the mitral valve, and securing them together using clasping, stitching, or suturing techniques. The free ends of the leaflets of the mitral valve also could be secured together utilizing a repair device which remains permanently implanted inside the atrium of the patient. Such a repair device shall be referred to hereinafter as a “fixation device.” The connection of the leaflets of the mitral valve together over a short length reduces the loss of tension in the leaflets thus allowing the remaining portions of the leaflets to have better coaptation and better perform the function of a one-way valve by preventing or reducing blood flow in the wrong direction.
Tricuspid valve prolapse, i.e. degeneration of tricuspid valve leaflets, is the most common cause of tricuspid regurgitation in North America. Many cases of regurgitation can be repaired by modifications of the original valve using a valvuloplasty procedure. However, valves that are heavily calcified or significantly compromised by disease may need to be replaced. The same approach taken in repairing the mitral valve has been tried for repairing the tricuspid valve using clasps such as the MitraClip® clasp, manufactured and sold by Abbott Vascular, Santa Clara, Calif. The tricuspid valve is similar to the mitral valve, hut it is more complex in that it has three leaflets, namely, the anterior leaflet, posterior leaflet and septal leaflet, which all converge at a common point of meeting near the center of the valve. The tricuspid valve prevents back flow of blood from the right ventricle into the right atrium during ventricular systole when it closes and allows blood to flow from the right atrium into the right ventricle during ventricular diastole when it opens. This valve can be weakened, for example, by drug abuse, endocarditis, rheumatic fever, heart disease and congenital abnormality. Tricuspid regurgitation, like mitral regurgitation, is typically caused by defective coaptation of the leaflets of the valve against each other and results in reduced pumping efficiency. Diagnosis of tricuspid regurgitation can be performed using visualization with transesophageal echocardiography or by echocardiography. In particular, defective leaflet coaptation and the site and direction of the regurgitant flow can be examined to evaluate likely modes of failure.
Methods for repairing the mitral valve normally do not apply conveniently to a method for repairing the tricuspid valve. One major difference is that while the mitral valve has only two leaflets extending generally parallel with each other and which need to be grasped simultaneously, the tricuspid valve has three leaflets that come to a common point of meeting. The mechanical problems involved in grasping all three leaflets simultaneously at a single point are far more complex than with the mitral valve because the operator is not presented with two elongated edges to grasp, but rather, with three triangulated points that must be grasped simultaneously. However, an interventionalist successfully performing this procedure can increase the tension in the leaflets to improve coaptation of the leaflets and help reduce regurgitation.
As used herein, the term “endovascular,” refers to procedure(s) of the present invention that are performed with interventional tools and supporting catheters and other equipment introduced to the heart chambers from the patient's arterial or venous vasculature remote from the heart. The interventional tools and other equipment may be introduced percutaneously, i.e., through an access sheath, or may be introduced via a surgical cut down, and then advanced from the remote access site through the vasculature until they reach the heart. In some instances, penetrations will be made interior to the heart, e.g., through the interatrial septum to provide a desired access route for the vascular instruments.
For these reasons, it would be desirable to provide alternative and additional methods, devices, and systems for performing the repair of mitral valves and other cardiac valves, such as the tricuspid valve, along with venous valves. Such methods, devices, and systems should preferably not require open chest access and be capable of being performed either endovascularly, i.e., using devices which are advanced to the heart from a point in the patient's vasculature remote from the heart or by a minimally invasive approach. Still more preferably, the methods, devices, and systems would be useful if the leaflets of the valve did not have to be grasped simultaneously by the fixation device. Additionally, it would be beneficial if two or more of the target tissue could be grasped by the fixation device at different locations which are not necessarily adjacent to each other but can nevertheless be drawn together to meet at or near a common location to close the gap formed on a damaged valve. Further, such devices and systems should provide features which allow repositioning and optional removal of the fixation device before the fixation device is permanently secured to the leaflets to ensure optimal placement. The present invention addresses these, and other needs.